I am looking to buy the AKG K240 Studio, but I saw several review on Amazon say that they break easily. Can anyone confirm the durability of these cans?

owned them for over a year now. A few days ago a girl kicked my headphones out of my hand for whatever reason and they hit a wall. The outer plastic cover on the housing fell off, and I got a look at the thickness of the housing... Hooooly fek. These are pretty tankish in all reality.
I then snapped the plastic cover thing back into place, yelled at the girl, then carried on with my day.

Obviously that's a pack of 50 and from amazon - get something similar (thin, black, no metal) from a local store.

And then actually replace the elastic. Yeah you'll need something like a tiny flathead screwdriver to pop the badges off, and a #1 philips to take the caps off, and a #2 to loose the headband from the cup so you can loop the new elastic through.

You might still want to open up your sextett, the foam that is inside of the cup is usually disintegrating and turning into a nasty gunk that can affect the sound quality (and make a mess). You can get replacement foams, but you could just rip the old ones out and see if you can hear a difference. For me it added a bit of clarity, and a good opportunity to change the elastics. If you do open them up, be careful and have a soldering iron available in case a wire comes loose. If you're interested, here is a source for factory replacements for the shot elastics and the inner foam ring.